The present invention relates to microphones for use in hearing aids. In particular, the present invention relates to microphone construction having a switching element capable of mechanically positioning the microphone into an omni-directional or directional mode.
Hearing aids that have the capabilities of a directional microphone and an omni-directional microphone are advantageous to the user. In certain situations an omni-directional microphone is preferred to a directional microphone and vice versa. For example, in a reverberant environment or in an environment that has background noise, a directional microphone will improve speech intelligibility. Directional microphones are also preferred when the sound source is close to the hearing aid user. In addition, attenuation of sounds coming from the rear provide better listening comfort in a noisy environment. Likewise, in other environments, directionality may not be needed, and in fact, may be a detriment.
For purposes of this application, by directional microphone is meant a microphone having two physically separated acoustic ports which acoustically relate back to opposite sides of a microphone diaphragm. In contrast, an omni-directional microphone has only one acoustic port which acoustically relates to only one side of the microphone diaphragm.
In the past, two microphones have been included in hearing aids, one an omni-directional microphone and the other a directional microphone. The hearing aid user may switch electronically from one to the other. David Preves, Directional Microphone Use in ITE Hearing Instruments, The Hearing Review, July 1997; Olson et al., Performance of SENSO C9 Directional, Widexpress, July 1997. This type of hearing aid construction has the disadvantage of the cost of two microphones and the added space that two microphones require.
There have also been attempts to provide a hearing aid that permits the user to select between directional or omni-directional modes using one microphone. Such hearing aid constructions are described in the following patents:
However, the hearing aid constructions in the above mentioned patents are not conducive to a miniature-in-the ear type of hearing aid construction since the switching mechanisms and the acoustic channels take up too much space.
The present invention includes a microphone construction for use in a hearing aid wherein a faceplate separates a switching mechanism from a microphone having first and second acoustic ports. The first and second acoustic ports are placed into acoustic relationships with first and second acoustic openings within the faceplate by first and second acoustic passages, respectively. The switching mechanism is positionable between a first position wherein the first and second acoustic ports are in an acoustically receptive state and a second position wherein either the first or second acoustic port is in an acoustically receptive state and the other acoustic port is in an acoustically unreceptive state.